1. Field of the Invention
The present invention relates to a photonic crystal light emitting device, and more particularly, to a photonic crystal light emitting device in which nano rod light emitting structures are disposed to define a photonic crystal, thereby enhancing light extraction efficiency.
2. Description of the Related Art
A semiconductor light emitting diode (LED) is a semiconductor device generating light of various colors when a current is supplied due to recombination of electrons and holes at a junction portion of p- and n-type semiconductors. This LED exhibits advantages such as longer useful life, lower power consumption, superior initial driving characteristics and high vibration resistance over a filament-based light emitting device. This has led to a continuous increase in demand. Particularly, of late, a group III nitride semiconductor capable of emitting light at a short wavelength such as blue light has been highlighted.
In such a semiconductor light emitting device, light generated from the active layer is reflected to different degrees according to an incident angle thereof when incident on an interface between air/GaN. Theoretically, when the light is incident at an incident angle of at least 26°, the light generated from the active layer is totally internally reflected and the totally internally reflected light is guided outward through sides, or absorbed or attenuated inside to mainly degrade emission efficiency.
Therefore, as one of methods for minimizing these problems and enhancing external light extraction efficiency, microstructures have been formed on a surface where the light exits outside.
As described above, a technology of reducing total reflection through the microstructures may increase external light extraction efficiency to some degree. However, there is required a structure for ensuring better emission efficiency. Particularly, in a case where the microstructures are formed on the p-type semiconductor layer by dry etching, chiefly, induction coupled plasma reactive ion etching (ICP-RIE), a semiconductor crystal structure for electrical operation, particularly a crystal structure near an active layer is severely impaired. Furthermore, at this time, an n-type donor is generated in a p-doped area to reduce a doping concentration of the p-type semiconductor layer. This phenomenon occurs not only locally but spreads longitudinally and horizontally. Accordingly, this may cause the semiconductor light emitting device to malfunction as an electrical driving device.